Fig. 367.—An Ant milking Aphides or Plant-lice (magnified).Fig. 367.—An Ant milking Aphides or Plant-lice (magnified).The possession of a flock of plant-lice is sometimes a subject of discord, and becomes acasus bellibetween two neighbouring ant-hills. But, usually, the war has for its object to make prisoners in other nests, and to carry off part of the inhabitants as slaves. This is the origin ofmixed ant-hills, which, independently of their natural founders, contain one or two foreign species, helots whom the conquerors have taken away from their birth-place, to make of them auxiliaries and slaves. In these mixed ant-hills the species imported occasionally exceed in number the original population, as it happenssometimes in those ships which are used in the slave trade, and on which the slaves are often found in greater numbers than the sailors composing the crew. The phalanx of ants reduced to a state of slavery pay all sorts of attentions to their masters. They lick them, brush them, caress them, carry them on their backs, feed them—good and faithful servants that they are—and even rear their progeny. The masters impose on their slaves all sorts of work. They only reserve for themselves the making of war. From time to time they undertake expeditions against some neighbouring ants' nest. If they are conquered and come back without bringing with them any prisoners, the slaves or auxiliaries are sulky to them, and will not allow them for some time to enter the nest. If, on the contrary, they return loaded with booty, they flatter them, give them food, and relieve them of their prisoners, which they lead away into the interior of the fortress. The warlike tribes, however, never carry off any other but the larvæ and nymphs of workers from the ant-hills they plunder. These young captives get used to their kidnappers: brought up in fear of their masters, they never think of abandoning them.Fig. 368.—Russet Ants (Polyergus rufescens).Two species constitute the warrior tribes which form societies mixed with the species they reduce to slavery. They are the Russet Ant (Fig. 368) and the Blood-red Ant (Fig. 369). They always attack the nests of the Ashy-black (Formica fusca) and the Miners.Fig. 369.—Blood-red AntFig. 369.—Blood-red Ant (Formica sanguinea).The Russet Ant has mandibles made for war; they appear cut out for struggling and fighting. The Blood-red Ants are less ferocious; they work themselves, and make none of those sweeping raids by which the Russet Ants depopulate the neighbouring ant-hills.What Peter Huber has done for bees, Francis Huber, his son, has done for the ants. It is from Francis Huber that we borrow the description which it remains for us to give of the habits of ants in times of war. He thus relates one of these expeditions, of which he was a witness:—"On the 17th of June, 1804," says he, "as I was walking in the environs of Geneva, between four and five in the afternoon, I saw at my feet a legion of largish russet ants crossing the road. They were marching in a body with rapidity, their troop occupied a space of from eight to ten feet long by three or four inches wide; in a few minutes they had entirely evacuated the road; they penetrated through a very thick hedge, and went into a meadow, whither I followed them. They wound their way along the turf, without straying, and their column remained always continuous, in spite of the obstacles which they had to surmount. Very soon they arrived near a nest of ashy-black ants, the dome of which rose among the grass, at twenty paces from the hedge. A few ants of this species were at the door of their habitation. As soon as they descried the army which was approaching, they threw themselves on those which were at the head of the cohort. The alarm spread at the same instant in the interior of the nest, and their companions rushed out in crowds from all the subterranean passages. The russet ants, the body of whose army was only two paces distant, hastened to arrive at the foot of the nest; the whole troop precipitated itself forward at the same time, and knocked the ashy-black ants head over heels, who, after a short but very smart combat, retired to the extremity of the habitation. The russet ants clambered up the sides of the hillock, flocked to the summit, and introduced themselves in great numbers into the first avenues; other groups worked with their teeth, making a lateral aperture. In this they succeeded, and the rest of the army penetrated through the breach into the besieged city. They did not make a long stay there; in three or four minutes the russet ants came out again in haste, by the same adits, carrying each one in its mouth a pupa or larva belonging to the conquered. They again took exactly the same road by which they had come, and followed each other in a straggling manner; their line was easily to be distinguished on the grass by the appearance which this multitude of white cocoons and larvæ, carried by as many russet-coloured ants, presented. They passed through the hedge a second time, crossedthe road, and then steered their course into a field of ripe wheat, whither, I regret to say, I was unable to follow them."[105]Huber adds that, having returned to the pillaged nest to examine it more closely, he saw some ashy-black workers bringing back to their home the few larvæ which they had succeeded in saving. Having later discovered the nest of these Amazons, which is the name he gives to the warrior ants, he found there many of the ashy-black ants living on very good terms with their kidnappers.The Amazons begin their expeditions at the end of June, during the hottest hours of the day. They come out in long files, eight or ten abreast, preceded by their scouts. These columns start at a run, in a straight line, and without feeling their way. They have no chieftain. The van is re-formed every moment. Those who are in front do not remain there; at the end of a certain time they go and range themselves in the rear, and are replaced by those which were behind. The whole troop is thus in constant communication through its entire length. Rarely does the expedition divide into two bodies. Arrived under the walls of the fortress, the column halts and masses itself into one corps. The assault is made with incredible impetuosity. In the twinkling of an eye the place is escaladed, taken by storm, and pillaged, and the ashy-black ants are either put to flight or led away into captivity. The same ant-hill may be invaded as many as three times running on the same day; but then the ashy-black ants, on their guard, have barricaded themselves in, and in that case the aggressors return home without pillaging them.Fig. 370.—Mining Ant (Formica cunicularia), male, worker, and female.The Mining Ants (Fig. 370) are less timid than the ashy-black; and, as they defend themselves with more energy, there are frequently deadly combats, and the field of battle is left covered with heads, legs, and limbs, scattered about here and there with the dead andwounded. The miners pursue the pillagers, and snatch their plunder from them. But they are sometimes driven back vigorously, and the russet ants gain their lair with the plunder.The tactics of the Red Ants (Formica sanguinea) differ from those of the russet. They only sally forth in small detachments, which begin by engaging in skirmishes with the scouts thrown out round the enemy's ant-hill. Couriers, despatched from time to time to the camp of the red ants, bring up reinforcements. When the troop feels itself sufficiently strong, it invades the nest of the ashy-black ants, and carries off their offspring, which the latter have not had time to secure. Sometimes, also, the red ants instal themselves in the nest whose inhabitants they have ejected, and transfer their own population to it. The motive for this emigration is that the old nest has become useless, or that it is exposed to some danger. The red ants are not the only ants which thus desert their birth-place. Many species abandon it likewise, for analogous motives, and construct elsewhere another dwelling, to which they transport all the population of the first nest.Fig. 372.—Mutilla Europæa, male and female.Fig. 371.—Philanthus triangulum.Fig. 372.—Mutilla Europæa, male and female.When we reflect on the habits of ants, we are forced to admit that intelligence and reason appear still more in their acts than in those of bees. The life of ants, as well as that of bees, as far as we are concerned, is an unintelligible enigma. The acts of animals, in general, are sometimes an abyss unfathomable to our reason. The Orientals say, "The last word may be written on man: on the elephant, never!" Let us add that they should no more say that the elephant will be an inexhaustible theme, but that the history of the ant will continue so always.The best-known genera of the Fossores, or Fossorial Hymenoptera, arePhilanthus(Fig. 371), which feeds its larvæ on bees, having first numbed them by its sting;PompilusandSphex, which attackspiders; andMutilla(Fig. 372), whose females resemble ants, being variegated with red and yellow, the males, being provided with wings and smaller in size, and black. TheMutillæare parasitical on solitary bees, their larvæ devouring their larvæ.Fig. 373.—A species of Pimpla.Fig. 374.—A species of Ophion.Other Hymenoptera lay their eggs under the skin of certain insects, especially when these are in the larva or caterpillar state, thus rendering service to agriculture by destroying a great number of noxious insects. In lieu of a sting they have an auger, intended to pierce the skin of their victims. It is thus that theIchneumonsintroduce their eggs under the skin of caterpillars. ThePimplas(Fig. 373), which belongs to this group, have a very long ovipositor, which, with its two appendages, constitute three lancets, and enable them to get at the larvæ in their retreats. TheOphions(Fig. 374)have a sickle-shaped abdomen. They lay their eggs on the skin of caterpillars, which they attack with the short cutting auger with which they are provided.Fig. 375.—Gall insect (Cynips quercusfolii).Fig. 376.—Oak Galls, produced byCynips quercusfolii.Fig. 377.—Interior of a Gall.TheCynips, or Gall-insects, are small black or tawny Hymenoptera, the females of which have an auger, rolled up spirally and hidden in a fissure of the abdomen, with which they prick the young shoots of plants. A peculiar liquid which they pour into the hole round the egg they have laid, causes an excrescence to grow, which is called a "gall." The larva is developed in the centre of this gall, and transformed into a pupa; and afterwards into a perfect insect, which makes its exit by a hole in the wall of its prison.Fig. 375represents the Cynips of the oak tree (Cynips quercusfolii), and Figs.376and377the galls it produces. The galls of the rose are hairy, and are sometimes called "Robin's Cushion." The gall-nut, rich in tannin, which is used in the manufacture of ink, is the produce of a foreign Cynips, which lives on an oak found in the East. Apples of Sodom, which travellers bring back from the shores of the Dead Sea, are large galls[106]full of dry dust and larvæ.TheUrocerataand theTenthredinetæform two tribes of insects,of which the first are of great size, have a cylindrical body, the abdomen being attached to the thorax in its whole breadth, without any pedicle.Fig. 378.—Sirex gigas.The insects of the genusSirex(Fig. 378), belonging to the former of these, lay their eggs in living wood, and their larvæ live for many years in the interior. They are to be met with in great numbers in forests of pine trees, and, according to Latreille, show themselves sometimes in such great numbers as to become an object of terror. The female of the Giant Sirex (Sirex gigas) possesses a long rectilinear auger. The mandibles of the larvæ are of great strength, and are even capable of perforating lead. This fact has been observed many times. In 1857 Marshal Vaillant presented to the Académie des Sciences some packets of cartridges containing balls which had been pierced through by the larvæ of the Sirex during the sojourn of the French troops in the Crimea. Some of these insects were still shut up in the gallery which they had hollowed out in the metal. M. Dumeril (and this was one of the last works of that venerable and learned naturalist) wrote a Report on this subject, in which were recorded many analogous instances. He quoted, as an example, that M. le Marquis de Brême, in 1844, showed to the Société Zoologique many cartridges in which the balls had been perforatedby the insects to a depth of about a quarter of an inch. These cartridges came from the arsenal of Turin. They had been placed in barrels made of larch wood, the inside of which had been attacked by the insects. It was discovered that it was after having left the wood that they had gnawed through the envelopes of the cartridges, and at last into the balls themselves. In 1833 Audouin presented to the Société Entomologique de France a plate of lead, from the roof of a building, on which this naturalist supposed that the larvæ of aCallidium[107]had made deep sinuosities, as they do in wood. Before this, parts of the leaden roofs at La Rochelle had been noticed not only gnawed, but pierced from one side to the other, by the larvæ ofBostrichus capucinus.[108]In 1844 M. Desmarest reported the erosion and perforation of sheets of lead by a species ofBostrichusand byCallidium. In 1843 M. Du Boys presented to the Société d'Agriculture of Limoges some stereotyped plates—composed, as is well-known, of a very hard alloy, formed of antimony and lead—which had been pierced and riddled with holes by two specimens of aBostrichus. The holes were a seventh of an inch in diameter by two inches in depth. The stereotypes were thus perforated, although they had been wrapped up in many folds of paper and cardboard. As the printing served for a work called "Les Fastes Militaires de la France," one may say that the brave soldiers received from an insect more wounds than their enemies had ever given them.To prove that these insects have really the power to perforate metals as others perforate and pass through woody matter, the entomologist of Limoges made the following experiments. He placed in a leaden box, the sides of which were thin, a living specimen of the Fire-coloured Lepture of Geoffroy (Callidium sanguineum), a Coleopteron which is commonly found in houses in France in winter, its larvæ being developed in great numbers in firewood. Above this box he fitted on another, also containing a specimen of this insect, which he shut in with a third box. A few days afterwards he separated the boxes. The middle one had been pierced through, and the two insects were found together, the one which was below having made a hole through which it might introduce itself into the middle box. M. Du Boys made a chemical experiment which enabled him to establish beyond a doubt that the insect which had gnawed the metal had not made it serve as its food. The dried body of one of these insects was analysed. After having immersed it in nitric acid it was completely burnt, and there could not befound in the ashes acted upon by the nitric acid the least trace of lead. This experiment proves that these insects had for their object only to escape from the galleries in which they were accidentally deposited in their larva state, and that it was not until they had undergone their complete transformation that they endeavoured to gain their liberty. Observations of the same kind were multiplied after the Report of M. Dumeril. The Académie des Sciences received, in the month of June, 1861, two Memoirs—one from M. Heriot, captain of artillery, the other from M. Bouteille, curator of the Museum of Natural History of Grenoble—containing many new observations on the perforation by insects of leaden balls contained in cartridges prepared for war. M. Milne-Edwards read to the Académie des Sciences a short Report on these works.The insect which had produced the perforations observed in the balls sent to the Crimea in 1857, and which M. Dumeril particularly studied, was theSirex juvencus, and had been taken from France in the wood forming the boxes which contained the cartridges. In the other case of which we are speaking, that is to say, of the cartridges which were sent in 1861 to the Académie by Captain Heriot and by M. Bouteille, the perforations had been produced by other species. M. Milne-Edwards, who found the insect that had caused this strange damage, had no trouble in recognising it as theSirex gigas, which, in its larva state, lives in the interior of old trees or pieces of wood, and which, after it has gone through all its metamorphoses, comes out of its retreat to reproduce its kind. To clear themselves a passage, they cut away with their mandibles the ligneous substances or other hard bodies they meet with on their road. It was in pursuing this object that the insects, imprisoned accidentally in the packets of cartridges when they were yet only in the larva state, must have attacked the leaden balls, as also the paper and the other matters which they met with on their road, and which opposed their passage. M. Bouteille proves, in his Memoir, that M. Dumeril has committed an error in saying that the perforating organ employed by theSirexto attack the leaden balls in the cartridges in the Crimea was the auger situated at the extremity of the abdomen of the female, and intended for cutting into that part of the wood where it is to lay its eggs. M. Bouteille has established, in fact, that they were not only the females which attacked the cartridges, but that the males, which have no auger, had occasioned the same damage.TheTenthredinetæare called "Saw-Flies," because the females are furnished with a double auger, notched like a saw, with which they cut into the branches in which they lay their eggs. The larvæof these insects have a striking resemblance to the caterpillars of Lepidoptera. They can only be distinguished from them by a great globular head, not hollowed out, and by their abdominal legs, in general to the number of more than ten. They are called false caterpillars (Fig. 379). Most of them, when touched, erect themselves and move about in a threatening manner. They spin a silken cocoon before changing into pupæ. TheLophyrus pini, which devours the leaves of pine trees, belongs to this family.Fig. 379.—Larva of a Saw-Fly.Fig. 379.—Larva of a Saw-Fly. (Tenthredo).Fig. 380.—Lophyrus pini.
Fig. 367.—An Ant milking Aphides or Plant-lice (magnified).Fig. 367.—An Ant milking Aphides or Plant-lice (magnified).
The possession of a flock of plant-lice is sometimes a subject of discord, and becomes acasus bellibetween two neighbouring ant-hills. But, usually, the war has for its object to make prisoners in other nests, and to carry off part of the inhabitants as slaves. This is the origin ofmixed ant-hills, which, independently of their natural founders, contain one or two foreign species, helots whom the conquerors have taken away from their birth-place, to make of them auxiliaries and slaves. In these mixed ant-hills the species imported occasionally exceed in number the original population, as it happenssometimes in those ships which are used in the slave trade, and on which the slaves are often found in greater numbers than the sailors composing the crew. The phalanx of ants reduced to a state of slavery pay all sorts of attentions to their masters. They lick them, brush them, caress them, carry them on their backs, feed them—good and faithful servants that they are—and even rear their progeny. The masters impose on their slaves all sorts of work. They only reserve for themselves the making of war. From time to time they undertake expeditions against some neighbouring ants' nest. If they are conquered and come back without bringing with them any prisoners, the slaves or auxiliaries are sulky to them, and will not allow them for some time to enter the nest. If, on the contrary, they return loaded with booty, they flatter them, give them food, and relieve them of their prisoners, which they lead away into the interior of the fortress. The warlike tribes, however, never carry off any other but the larvæ and nymphs of workers from the ant-hills they plunder. These young captives get used to their kidnappers: brought up in fear of their masters, they never think of abandoning them.
Fig. 368.—Russet Ants (Polyergus rufescens).
Two species constitute the warrior tribes which form societies mixed with the species they reduce to slavery. They are the Russet Ant (Fig. 368) and the Blood-red Ant (Fig. 369). They always attack the nests of the Ashy-black (Formica fusca) and the Miners.
Fig. 369.—Blood-red AntFig. 369.—Blood-red Ant (Formica sanguinea).
The Russet Ant has mandibles made for war; they appear cut out for struggling and fighting. The Blood-red Ants are less ferocious; they work themselves, and make none of those sweeping raids by which the Russet Ants depopulate the neighbouring ant-hills.
What Peter Huber has done for bees, Francis Huber, his son, has done for the ants. It is from Francis Huber that we borrow the description which it remains for us to give of the habits of ants in times of war. He thus relates one of these expeditions, of which he was a witness:—"On the 17th of June, 1804," says he, "as I was walking in the environs of Geneva, between four and five in the afternoon, I saw at my feet a legion of largish russet ants crossing the road. They were marching in a body with rapidity, their troop occupied a space of from eight to ten feet long by three or four inches wide; in a few minutes they had entirely evacuated the road; they penetrated through a very thick hedge, and went into a meadow, whither I followed them. They wound their way along the turf, without straying, and their column remained always continuous, in spite of the obstacles which they had to surmount. Very soon they arrived near a nest of ashy-black ants, the dome of which rose among the grass, at twenty paces from the hedge. A few ants of this species were at the door of their habitation. As soon as they descried the army which was approaching, they threw themselves on those which were at the head of the cohort. The alarm spread at the same instant in the interior of the nest, and their companions rushed out in crowds from all the subterranean passages. The russet ants, the body of whose army was only two paces distant, hastened to arrive at the foot of the nest; the whole troop precipitated itself forward at the same time, and knocked the ashy-black ants head over heels, who, after a short but very smart combat, retired to the extremity of the habitation. The russet ants clambered up the sides of the hillock, flocked to the summit, and introduced themselves in great numbers into the first avenues; other groups worked with their teeth, making a lateral aperture. In this they succeeded, and the rest of the army penetrated through the breach into the besieged city. They did not make a long stay there; in three or four minutes the russet ants came out again in haste, by the same adits, carrying each one in its mouth a pupa or larva belonging to the conquered. They again took exactly the same road by which they had come, and followed each other in a straggling manner; their line was easily to be distinguished on the grass by the appearance which this multitude of white cocoons and larvæ, carried by as many russet-coloured ants, presented. They passed through the hedge a second time, crossedthe road, and then steered their course into a field of ripe wheat, whither, I regret to say, I was unable to follow them."[105]
Huber adds that, having returned to the pillaged nest to examine it more closely, he saw some ashy-black workers bringing back to their home the few larvæ which they had succeeded in saving. Having later discovered the nest of these Amazons, which is the name he gives to the warrior ants, he found there many of the ashy-black ants living on very good terms with their kidnappers.
The Amazons begin their expeditions at the end of June, during the hottest hours of the day. They come out in long files, eight or ten abreast, preceded by their scouts. These columns start at a run, in a straight line, and without feeling their way. They have no chieftain. The van is re-formed every moment. Those who are in front do not remain there; at the end of a certain time they go and range themselves in the rear, and are replaced by those which were behind. The whole troop is thus in constant communication through its entire length. Rarely does the expedition divide into two bodies. Arrived under the walls of the fortress, the column halts and masses itself into one corps. The assault is made with incredible impetuosity. In the twinkling of an eye the place is escaladed, taken by storm, and pillaged, and the ashy-black ants are either put to flight or led away into captivity. The same ant-hill may be invaded as many as three times running on the same day; but then the ashy-black ants, on their guard, have barricaded themselves in, and in that case the aggressors return home without pillaging them.
Fig. 370.—Mining Ant (Formica cunicularia), male, worker, and female.
The Mining Ants (Fig. 370) are less timid than the ashy-black; and, as they defend themselves with more energy, there are frequently deadly combats, and the field of battle is left covered with heads, legs, and limbs, scattered about here and there with the dead andwounded. The miners pursue the pillagers, and snatch their plunder from them. But they are sometimes driven back vigorously, and the russet ants gain their lair with the plunder.
The tactics of the Red Ants (Formica sanguinea) differ from those of the russet. They only sally forth in small detachments, which begin by engaging in skirmishes with the scouts thrown out round the enemy's ant-hill. Couriers, despatched from time to time to the camp of the red ants, bring up reinforcements. When the troop feels itself sufficiently strong, it invades the nest of the ashy-black ants, and carries off their offspring, which the latter have not had time to secure. Sometimes, also, the red ants instal themselves in the nest whose inhabitants they have ejected, and transfer their own population to it. The motive for this emigration is that the old nest has become useless, or that it is exposed to some danger. The red ants are not the only ants which thus desert their birth-place. Many species abandon it likewise, for analogous motives, and construct elsewhere another dwelling, to which they transport all the population of the first nest.
When we reflect on the habits of ants, we are forced to admit that intelligence and reason appear still more in their acts than in those of bees. The life of ants, as well as that of bees, as far as we are concerned, is an unintelligible enigma. The acts of animals, in general, are sometimes an abyss unfathomable to our reason. The Orientals say, "The last word may be written on man: on the elephant, never!" Let us add that they should no more say that the elephant will be an inexhaustible theme, but that the history of the ant will continue so always.
The best-known genera of the Fossores, or Fossorial Hymenoptera, arePhilanthus(Fig. 371), which feeds its larvæ on bees, having first numbed them by its sting;PompilusandSphex, which attackspiders; andMutilla(Fig. 372), whose females resemble ants, being variegated with red and yellow, the males, being provided with wings and smaller in size, and black. TheMutillæare parasitical on solitary bees, their larvæ devouring their larvæ.
Other Hymenoptera lay their eggs under the skin of certain insects, especially when these are in the larva or caterpillar state, thus rendering service to agriculture by destroying a great number of noxious insects. In lieu of a sting they have an auger, intended to pierce the skin of their victims. It is thus that theIchneumonsintroduce their eggs under the skin of caterpillars. ThePimplas(Fig. 373), which belongs to this group, have a very long ovipositor, which, with its two appendages, constitute three lancets, and enable them to get at the larvæ in their retreats. TheOphions(Fig. 374)have a sickle-shaped abdomen. They lay their eggs on the skin of caterpillars, which they attack with the short cutting auger with which they are provided.
TheCynips, or Gall-insects, are small black or tawny Hymenoptera, the females of which have an auger, rolled up spirally and hidden in a fissure of the abdomen, with which they prick the young shoots of plants. A peculiar liquid which they pour into the hole round the egg they have laid, causes an excrescence to grow, which is called a "gall." The larva is developed in the centre of this gall, and transformed into a pupa; and afterwards into a perfect insect, which makes its exit by a hole in the wall of its prison.Fig. 375represents the Cynips of the oak tree (Cynips quercusfolii), and Figs.376and377the galls it produces. The galls of the rose are hairy, and are sometimes called "Robin's Cushion." The gall-nut, rich in tannin, which is used in the manufacture of ink, is the produce of a foreign Cynips, which lives on an oak found in the East. Apples of Sodom, which travellers bring back from the shores of the Dead Sea, are large galls[106]full of dry dust and larvæ.
TheUrocerataand theTenthredinetæform two tribes of insects,of which the first are of great size, have a cylindrical body, the abdomen being attached to the thorax in its whole breadth, without any pedicle.
Fig. 378.—Sirex gigas.
The insects of the genusSirex(Fig. 378), belonging to the former of these, lay their eggs in living wood, and their larvæ live for many years in the interior. They are to be met with in great numbers in forests of pine trees, and, according to Latreille, show themselves sometimes in such great numbers as to become an object of terror. The female of the Giant Sirex (Sirex gigas) possesses a long rectilinear auger. The mandibles of the larvæ are of great strength, and are even capable of perforating lead. This fact has been observed many times. In 1857 Marshal Vaillant presented to the Académie des Sciences some packets of cartridges containing balls which had been pierced through by the larvæ of the Sirex during the sojourn of the French troops in the Crimea. Some of these insects were still shut up in the gallery which they had hollowed out in the metal. M. Dumeril (and this was one of the last works of that venerable and learned naturalist) wrote a Report on this subject, in which were recorded many analogous instances. He quoted, as an example, that M. le Marquis de Brême, in 1844, showed to the Société Zoologique many cartridges in which the balls had been perforatedby the insects to a depth of about a quarter of an inch. These cartridges came from the arsenal of Turin. They had been placed in barrels made of larch wood, the inside of which had been attacked by the insects. It was discovered that it was after having left the wood that they had gnawed through the envelopes of the cartridges, and at last into the balls themselves. In 1833 Audouin presented to the Société Entomologique de France a plate of lead, from the roof of a building, on which this naturalist supposed that the larvæ of aCallidium[107]had made deep sinuosities, as they do in wood. Before this, parts of the leaden roofs at La Rochelle had been noticed not only gnawed, but pierced from one side to the other, by the larvæ ofBostrichus capucinus.[108]In 1844 M. Desmarest reported the erosion and perforation of sheets of lead by a species ofBostrichusand byCallidium. In 1843 M. Du Boys presented to the Société d'Agriculture of Limoges some stereotyped plates—composed, as is well-known, of a very hard alloy, formed of antimony and lead—which had been pierced and riddled with holes by two specimens of aBostrichus. The holes were a seventh of an inch in diameter by two inches in depth. The stereotypes were thus perforated, although they had been wrapped up in many folds of paper and cardboard. As the printing served for a work called "Les Fastes Militaires de la France," one may say that the brave soldiers received from an insect more wounds than their enemies had ever given them.
To prove that these insects have really the power to perforate metals as others perforate and pass through woody matter, the entomologist of Limoges made the following experiments. He placed in a leaden box, the sides of which were thin, a living specimen of the Fire-coloured Lepture of Geoffroy (Callidium sanguineum), a Coleopteron which is commonly found in houses in France in winter, its larvæ being developed in great numbers in firewood. Above this box he fitted on another, also containing a specimen of this insect, which he shut in with a third box. A few days afterwards he separated the boxes. The middle one had been pierced through, and the two insects were found together, the one which was below having made a hole through which it might introduce itself into the middle box. M. Du Boys made a chemical experiment which enabled him to establish beyond a doubt that the insect which had gnawed the metal had not made it serve as its food. The dried body of one of these insects was analysed. After having immersed it in nitric acid it was completely burnt, and there could not befound in the ashes acted upon by the nitric acid the least trace of lead. This experiment proves that these insects had for their object only to escape from the galleries in which they were accidentally deposited in their larva state, and that it was not until they had undergone their complete transformation that they endeavoured to gain their liberty. Observations of the same kind were multiplied after the Report of M. Dumeril. The Académie des Sciences received, in the month of June, 1861, two Memoirs—one from M. Heriot, captain of artillery, the other from M. Bouteille, curator of the Museum of Natural History of Grenoble—containing many new observations on the perforation by insects of leaden balls contained in cartridges prepared for war. M. Milne-Edwards read to the Académie des Sciences a short Report on these works.
The insect which had produced the perforations observed in the balls sent to the Crimea in 1857, and which M. Dumeril particularly studied, was theSirex juvencus, and had been taken from France in the wood forming the boxes which contained the cartridges. In the other case of which we are speaking, that is to say, of the cartridges which were sent in 1861 to the Académie by Captain Heriot and by M. Bouteille, the perforations had been produced by other species. M. Milne-Edwards, who found the insect that had caused this strange damage, had no trouble in recognising it as theSirex gigas, which, in its larva state, lives in the interior of old trees or pieces of wood, and which, after it has gone through all its metamorphoses, comes out of its retreat to reproduce its kind. To clear themselves a passage, they cut away with their mandibles the ligneous substances or other hard bodies they meet with on their road. It was in pursuing this object that the insects, imprisoned accidentally in the packets of cartridges when they were yet only in the larva state, must have attacked the leaden balls, as also the paper and the other matters which they met with on their road, and which opposed their passage. M. Bouteille proves, in his Memoir, that M. Dumeril has committed an error in saying that the perforating organ employed by theSirexto attack the leaden balls in the cartridges in the Crimea was the auger situated at the extremity of the abdomen of the female, and intended for cutting into that part of the wood where it is to lay its eggs. M. Bouteille has established, in fact, that they were not only the females which attacked the cartridges, but that the males, which have no auger, had occasioned the same damage.
TheTenthredinetæare called "Saw-Flies," because the females are furnished with a double auger, notched like a saw, with which they cut into the branches in which they lay their eggs. The larvæof these insects have a striking resemblance to the caterpillars of Lepidoptera. They can only be distinguished from them by a great globular head, not hollowed out, and by their abdominal legs, in general to the number of more than ten. They are called false caterpillars (Fig. 379). Most of them, when touched, erect themselves and move about in a threatening manner. They spin a silken cocoon before changing into pupæ. TheLophyrus pini, which devours the leaves of pine trees, belongs to this family.